TrustworthinessSafetyTransparencycs.CL
Query-Level Uncertainty in Large Language Models
Lihu Chen, Gerard de Melo, Fabian M. Suchanek, Gaël Varoquaux
June 11, 2025
arXiv.org
16 citations
Key Takeaways
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LLMs need to know their limits: The paper addresses a critical responsibility issue—AI models should be able to recognize when they don't know something rather than confidently providing incorrect answers. This self-awareness is essential for trustworthy AI systems.
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Early detection saves resources and improves reliability: The proposed "Internal Confidence" method can assess whether an LLM can answer a question before generating a response, avoiding wasted computation. This allows the system to route difficult questions to better tools (like retrieval systems) or admit uncertainty upfront, rather than producing potentially false information.
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The method works without additional training: Unlike many AI safety approaches that require expensive retraining, Internal Confidence operates on existing models by analyzing their internal layer-by-layer confidence signals, making it practical to implement across different LLM systems.
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Real-world efficiency gains demonstrated: Testing on factual questions and math problems showed the method reduces computational costs in "adaptive inference" scenarios (where the system chooses different strategies for different questions) while maintaining answer quality—meaning organizations can deploy more responsible AI without sacrificing performance.
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Uncertainty detection enables responsible AI workflows: By identifying knowledge boundaries, this approach enables key safety mechanisms like having models ask for help via retrieval systems, taking more time to think through hard problems, or appropriately declining to answer—all critical behaviors for AI systems deployed in high-stakes settings.
Abstract
It is important for Large Language Models (LLMs) to be aware of the boundary of their knowledge, distinguishing queries they can confidently answer from those that lie beyond their capabilities. Such awareness enables models to perform adaptive inference, such as invoking retrieval-augmented generation (RAG), engaging in slow and deep thinking, or abstaining from answering when appropriate. These mechanisms are key to developing efficient and trustworthy AI. In this work, we propose a method to detect knowledge boundaries via Query-Level Uncertainty, which estimates if a model is capable of answering a given query before generating any tokens, thus avoiding the generation cost. To this end, we propose a novel, training-free method called Internal Confidence, which leverages self-evaluations across layers and tokens to provide a reliable signal of uncertainty. Empirical studies on both factual question answering and mathematical reasoning tasks demonstrate that our Internal Confidence outperforms several baselines in quality of confidence while being computationally cheaper. Furthermore, we demonstrate its benefits in adaptive inference settings, showing that for RAG and model cascading it reduces inference costs while preserving overall performance.
ICLR 2026
Paper Info
arXiv ID2506.09669
PublishedJune 11, 2025
RevisedMarch 4, 2026
Citations
16
Relevance82%
VenuearXiv.org
TypeJournalArticle
Categorycs.CL
Responsible AI Topics
TrustworthinessSafetyTransparency
Links
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